Significance The limbic system includes structures such as the hippocampal formation that is intimately involved in normal memory function and the amygdala that is involved in emotion and in social behavior. Pathology of these regions is a hallmark of a variety of disorders including Alzheimer's disease, epilepsy, schizophrenia and a variety of affective disorders. Objectives This program undertakes a broad range of neuroanatomical studies to determine the major intrinsic and extrinsic connections of the hippocampal formation and amygdaloid complex. It also employs immunohistochemical and molecular neuroanatomic techniques to study the chemical neuroanatomy of these regions. Results Recent studies have demonstrated that the main subcortical pathway of the amygdala uses the inhibitory neurotransmitter GABA. Other publications have mapped the GABAergic systems within the hippocampal formation and have studied the cytoarchitectonic and connectional attributes of the retrosplenial cortex. Future Directions A unique in vitro electrophysiology laboratory has been established which allows detailed analyses of the microcircuitry of the monkey brain. We will also be extending our studies of the monkey medial temporal lobe to studies of the human brain. KEY WORDS hippocampus, amygdala, electrophysiology, neuroanatomy FUNDING NIH Grants MH41479 & NS16980